gabriele giovannini marcello giroletti gregory b. taylor dipartimento di astronomia, bologna...
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Gabriele GiovanniniMarcello GirolettiGregory B. Taylor
Dipartimento di Astronomia, Bologna UniversityIstituto di Radioastronomia, INAF Bologna
Dept. of Physics and Astronomy, Univ. of New Mexico
The jet of Markarian 501 from the sub-parsec to the kpc scale
z = 0.034 1mas = 0.67 pc
Tavecchio et al. 2001
From NED
Mkn 501 –Large Scale
VLA
20 kpc
Symmetric structureSymmetric structure
Jets are no more relativisticsJets are no more relativistics
on 10 kpc scale on 10 kpc scale
Koolgaard et al. 1992
1.5 kpc1.5 kpc
VLA A array at 1.4 GHz
At 2 arcsecond β cosθ > 0.36
At 1 arcsecond β cosθ > 0.63
1.5 kpc1.5 kpc
VLA B array (Cassaro et al. 1999)
HPBW = 9x5 mas
35 pc
At 100 mas: β cosθ > 0.61
At 50 mas: β cosθ > 0.77
The jet shows a complex and continuous morphology with manysharp bends before undergoing a last turn in the PA of the kpc scale structure. The jet is clearly limb brightened.At 10 mas: β cosθ > 0.92
15 pc
Evident limb-brightened structure beginning very near to the core and visible up to 100 mas from it. It is interpreted as evidence of a velocity structure.No proper motion has been found comparing 9 different epochs from 1995.29 to 1999.55. Compact structures are resolved and complex in high resolution images
22 GHz
1.6 GHz VSOP
1.5 pc1.5 pc
3 pc3 pc
10 pc10 pc
22 GHz22 GHz
Thanks to the global mm VLBI network:VLBA (7 telescopes), Eb, Plateau de Bure,Pico Veleta, Onsala, Metsahovi
0.20.2 pcpc
A radio core + one sided jet is visible in recent VLBI observations at 86.2 GHz with a linear resolution of0.08 x 0.13 pc (HPBW) Giroletti et al. in prep.
Core: unresolved at 86 GHz size lower than 0.03 pc (gaussian fit)
1 Rs = 0.001 pc (M = 109 Mo)
High frequency spectrum is steep with a turnover at about 8.4 GHz.
It implies a magnetic field in the range 0.01 – 0.03 G and that inside
the “core” a structure is present
Question: why the jet brightness is so low
in the 86 GHz image?
Steepening because of high magnetic field?
We do not have polarization information
Gabuzda et al. 2004: B fields are dominated
by the toroidal component.
0.08 pc
Better images to:
find the core position
measure the jet dynamics
(starting velocity and
acceleration + velocity
structure)
M87
at 86 GHz (Krichbaum et al. 2006)
at 43 GHz (VLBA) (Ly et al. 2007)
MKN501 at 86 GHz
Jet velocity and orientation from data:
High velocity jet with Γ =15 and θ = 4o (δ 15) in the gamma-ray region (< 0.02 mas < 0.02 pc) – from high frequency emission, gamma-ray variability, and SED (SSC models)
In the radio jet region the jet orientation move from 4o to 10o - 15o to explain the limb-brightened structure radio structure and Γ decrease to 10 (δ 2.6) at 30 - 40 mas from the core (80-120 pc)
The jet velocity decrease is low: from HSA data we estimate relativistic jets (v > 0.6 c at 1” from the core)
At 5” (10 kpc de-projected) the jet is no more relativistic (Γ= 1.02 v = 0.2c) as expected from FR I jet velocities
Jet PA not constant for unknown reasons
Observational data are in agreement with a simple adiabatic model if the
magnetic field is mostly perpendicular to the jet (a parallel field predicts a
too fast velocity decrease with respect to the j cj ratio)
25
20
15
10
5
Adiabatic model in the case of relativistic motion discussed by Baum et al. 1997. See also
Cotton et al. 1999, and Giroletti et al. 2004
Jet initial velocity
0.998 c
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